Nano-materials and nanotechnologies are fast becoming a force in semiconductor technology. Nano-materials are generally described as materials whose fabrication scale is so small that the molecular properties of the materials begin to predominate over the bulk properties of the material.
In particular, carbon nanotube technologies are becoming a significant factor in electronic device construction. In one implementation, nano-materials comprise nanotubes. Single-wall carbon nanotubes (SWCNT) are quasi-one dimensional nanowires, which exhibit either metallic or semiconductor properties depending upon their chirality and radius. In some implementations, such carbon nanotubes are in the range of about 3-50 nanometers (nm) in diameter and several micrometers (μm) long. Single-wall nanotubes have been demonstrated as both semiconductor layers in thin film transistors as well as metallic interconnects between metal layers. Applications of carbon nanotube (CNT) electronic devices are compounding almost daily. Most notably are new CMOS transistors, non-volatile memory and backend interconnects.
Nanotubes can be deposited in layers or ribbons of materials to, for example, construct electrical connections or nanowires. One new area of implementation is that of non-volatile memory devices. One such application is described in U.S. Pat. No. 6,919,592 which is directed to hybrid circuits using nanotube electromechanical memory. This reference is hereby incorporated by reference for all purposes. This reference also describes in detail the methods of forming nanotube layers as known to those having ordinary skill in the art. A fuller description of the operation of these devices can be obtained in these and other related references.
The inventors point out that this is just but one of a myriad of potential applications for this extremely versatile technology. In many applications, the nanotubes form conductive layers that are is deposited onto substrates. During such fabrication of electrical structures, alignment issues for the deposition of nanotube layers become important.
FIGS. 1(a) and 1(b) depict a perfectly aligned carbon nanotube (CNT) layer 101 aligned against the side 102 of a metallization line 103. The problem with forming this structure using existing technologies is that it is dependent on extreme adherence to very narrow tolerances. Using alignment marks the CNT patterns are aligned to the metallization pattern to effect the alignment of the two structures.
In practice such alignment fails a significant portion of the time due to alignment errors. What is needed is a robust manufacturable process for aligning nanotubes with an associated metallization layer.